/*
 * Copyright (c) 2012, 2020, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
 * derivative works of, display, perform, and distribute the Software and make,
 * use, sell, offer for sale, import, export, have made, and have sold the
 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package com.oracle.truffle.jx.nodes.controlflow;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.nodes.*;
import com.oracle.truffle.api.nodes.BlockNode.ElementExecutor;
import com.oracle.truffle.jx.nodes.JXStatementNode;
import com.oracle.truffle.jx.nodes.local.JXWriteLocalVariableNode;
import com.oracle.truffle.jx.nodes.local.SLScopedNode;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/** A statement node that just executes a list of other statements. */
@NodeInfo(shortName = "block", description = "The node implementing a source code block")
public final class SLBlockNode extends JXStatementNode
    implements BlockNode.ElementExecutor<JXStatementNode> {

  /**
   * The block of child nodes. Using the block node allows Truffle to split the block into multiple
   * groups for compilation if the method is too big. This is an optional API. Alternatively, you
   * may just use your own block node, with a {@link
   * com.oracle.truffle.api.nodes.Node.Children @Children} field. However, this prevents Truffle
   * from compiling big methods, so these methods might fail to compile with a compilation bailout.
   */
  @Child private BlockNode<JXStatementNode> block;

  /**
   * All declared variables visible from this block (including all parent blocks). Variables
   * declared in this block only are from zero index up to {@link #parentBlockIndex} (exclusive).
   */
  @CompilationFinal(dimensions = 1)
  private JXWriteLocalVariableNode[] writeNodesCache;

  /** Index of the parent block's variables in the {@link #writeNodesCache list of variables}. */
  @CompilationFinal private int parentBlockIndex = -1;

  public SLBlockNode(JXStatementNode[] bodyNodes) {
    /*
     * Truffle block nodes cannot be empty, that is why we just set the entire block to null if
     * there are no elements. This is good practice as it safes memory.
     */
    this.block = bodyNodes.length > 0 ? BlockNode.create(bodyNodes, this) : null;
  }

  /**
   * Execute all block statements. The block node makes sure that {@link ExplodeLoop full unrolling}
   * of the loop is triggered during compilation. This allows the {@link
   * JXStatementNode#executeVoid} method of all children to be inlined.
   */
  @Override
  public void executeVoid(VirtualFrame frame) {
    if (this.block != null) {
      this.block.executeVoid(frame, BlockNode.NO_ARGUMENT);
    }
  }

  public List<JXStatementNode> getStatements() {
    if (block == null) {
      return Collections.emptyList();
    }
    return Collections.unmodifiableList(Arrays.asList(block.getElements()));
  }

  /**
   * Truffle nodes don't have a fixed execute signature. The {@link ElementExecutor} interface tells
   * the framework how block element nodes should be executed. The executor allows to add a custom
   * exception handler for each element, e.g. to handle a specific {@link ControlFlowException} or
   * to pass a customizable argument, that allows implement startsWith semantics if needed. For SL
   * we don't need to pass any argument as we just have plain block nodes, therefore we pass {@link
   * BlockNode#NO_ARGUMENT}. In our case the executor does not need to remember any state so we
   * reuse a singleton instance.
   */
  @Override
  public void executeVoid(VirtualFrame frame, JXStatementNode node, int index, int argument) {
    node.executeVoid(frame);
  }

  /**
   * All declared local variables accessible in this block. Variables declared in parent blocks are
   * included.
   */
  public JXWriteLocalVariableNode[] getDeclaredLocalVariables() {
    JXWriteLocalVariableNode[] writeNodes = writeNodesCache;
    if (writeNodes == null) {
      CompilerDirectives.transferToInterpreterAndInvalidate();
      writeNodesCache = writeNodes = findDeclaredLocalVariables();
    }
    return writeNodes;
  }

  public int getParentBlockIndex() {
    return parentBlockIndex;
  }

  private JXWriteLocalVariableNode[] findDeclaredLocalVariables() {
    if (block == null) {
      return new JXWriteLocalVariableNode[] {};
    }
    // Search for those write nodes, which declare variables
    List<JXWriteLocalVariableNode> writeNodes = new ArrayList<>(4);
    int[] varsIndex = new int[] {0};
    NodeUtil.forEachChild(
        block,
        new NodeVisitor() {
          @Override
          public boolean visit(Node node) {
            if (node instanceof WrapperNode) {
              NodeUtil.forEachChild(node, this);
              return true;
            }
            if (node instanceof SLScopedNode) {
              SLScopedNode scopedNode = (SLScopedNode) node;
              scopedNode.setVisibleVariablesIndexOnEnter(varsIndex[0]);
            }
            // Do not enter any nested blocks.
            if (!(node instanceof SLBlockNode)) {
              NodeUtil.forEachChild(node, this);
            }
            // Write to a variable is a declaration unless it exists already in a parent scope.
            if (node instanceof JXWriteLocalVariableNode) {
              JXWriteLocalVariableNode wn = (JXWriteLocalVariableNode) node;
              if (wn.isDeclaration()) {
                writeNodes.add(wn);
                varsIndex[0]++;
              }
            }
            if (node instanceof SLScopedNode) {
              SLScopedNode scopedNode = (SLScopedNode) node;
              scopedNode.setVisibleVariablesIndexOnExit(varsIndex[0]);
            }
            return true;
          }
        });
    Node parentBlock = findBlock();
    JXWriteLocalVariableNode[] parentVariables = null;
    if (parentBlock instanceof SLBlockNode) {
      parentVariables = ((SLBlockNode) parentBlock).getDeclaredLocalVariables();
    }
    JXWriteLocalVariableNode[] variables =
        writeNodes.toArray(new JXWriteLocalVariableNode[writeNodes.size()]);
    parentBlockIndex = variables.length;
    if (parentVariables == null || parentVariables.length == 0) {
      return variables;
    } else {
      int parentVariablesIndex = ((SLBlockNode) parentBlock).getParentBlockIndex();
      int visibleVarsIndex = getVisibleVariablesIndexOnEnter();
      int allVarsLength =
          variables.length + visibleVarsIndex + parentVariables.length - parentVariablesIndex;
      JXWriteLocalVariableNode[] allVariables = Arrays.copyOf(variables, allVarsLength);
      System.arraycopy(parentVariables, 0, allVariables, variables.length, visibleVarsIndex);
      System.arraycopy(
          parentVariables,
          parentVariablesIndex,
          allVariables,
          variables.length + visibleVarsIndex,
          parentVariables.length - parentVariablesIndex);
      return allVariables;
    }
  }
}
